Method and apparatus for studying sound



July 3, 1934. F, M. ROBB 1,964,929r

METHOD AND APPARATUS FOR STUDYING SOUND Filed Feb. 2l 1930 INVENTOR Brnk Morse Robb Patented July 3, 1934 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR STUDYING SOUND 2 Claims.

.I This invention relates to a method and apparatus for studying sound.

It is among the objects of the present invention to provide a method of propagating sound 1 5 waves in accordance with the outline configuration of a physical body. f A further object of the invention is to provide a method of producing sound waves in response to the shadow of a physical body.

A further object of the present invention is to provide a method of propagating sound waves through the superimposition of a shadow of a wave form upon a light-sensitive medium.

Another object of the present invention is to 15 provide an apparatus for carrying out the methods above outlined.

A further object of the invention is to provide an apparatus of the class described by means of which any physical body may be utilized for 120 forming the wave front shadow.

\ A still further object of the invention is to provide an apparatus of the class described, by means of which a wave form may be used to modulate electrical current by the provision of means for superilnposing upon a light-sensitive medium, the shadow of successive portions of the Wave front.

Numerous other objects and features of the present invention will be apparent from a con- '30 sideration of the following specification taken in conjunction with the accompanying drawing, in which- Figure 1 is a diagrammatic illustration of one preferred form of the present invention.

Fig. 2 is a front plan view of the cabinet as shown in Fig. 1;

Fig. 3 is a view illustrating various sound wave formations;

Fig. 4 is a view similar to Fig. 1, of a modified form of the invention, utilizing a slotted drum;

Fig. 5 is a top plan view of a further modification, utilizing a moving belt;

Fig. 6 is a fragmentary plan view of the moving belt used in Fig. 5;

Fig. 'I is a view similar to Fig. 6, but of a portion of a slotted disc;

And Fig. 8 is similar to Fig. 7, but shows a view of the slotted drum.

Like numerals refer to like parts throughout the several views.

Referring more particularly to Fig. 1 of the drawing, the apparatus forming part of the present invention includes a suitable source of illumination as indicated at 10, which may be of any desired type of electrically or otherwise energized4 lamp, preferably including a lens for focusing the light rays upon the desired portion of the associated cabinet. The cabinet indicated at 1l,

is provided with a front 12 which is apertured as 60. at 13, the aperture 13 generally extending transversely of the cabinet, the ends of the aperture being on lines radiating from the center` of the front and the sides being curved along circular lines, the center of curvature of which is coin- 65. cident with a point from which the lines of the ends radiate. It will be understood that the specific configuration of the aperture 13 is preferably as herein shown and described, but that the invention is Anot specifically limited to such con-.70 figuration.

Within the cabinet 11, a suitable light-sensitive element 14 is provided, which is preferably as shown, in the form of a photo-electric cell and which is electrically associated with an arn- 75 plifier indicated at 15, from which electrical conductors 16 extend for association with a suitable sound propagating instrument 17. In line with the photoelectric cell 14 and the aperture 13, a suitable concentrating lens 18 is pro- 80 vided. For controlling the light which enters the aperture 13 and which is concentrated by the lens 18 for impinging upon the photoelectric cell 14, a disk 20 is rovided, mounted on the shaft 21 and adapted for rotation by the motor 85 22. Referring more particularly to Fig. 2, in which the disk 20 is shown in dotted lines, it will be noted that the peripheral edge of the disk is provided with a plurality of radially positioned slots 23.

In the modification shown in Fig. 4 there is employed a motor 26 having a vertically-rotating shaft which carries a slotted drum 27, adapted to be rotated about the center of a suitable base in front of the aperture 13.

In the modification shown in Fig. 5, which is a top plan View, a slotted ribbon 28 moving between suitable rollers 2.9-29 is utilized for the same purpose as the disk 20 in Fig. l and drum 27 in Fig. 4.

An alternative arrangement involves the use of holes instead of slots in the moving disk 20, Fig. 1, the wave form being cast on the window in bands of varying degrees of light and shadow, as illustrated in Fig. 8, the same as the sound 105 waves are represented by varying degrees of silver deposits in a talking moving picture film.

In connection with the use of moving belt 28, Fig. 5, there would result a straight-across movement of the light band and graphs of sound waves 1.10

to be reproduced could be made on straight lines instead of on the circumference of a circle, which would of course be necessary with the slotted disk arrangement.

In the operation of the device, it will be seen that light waves propagated by the lamp 10, are directed to the aperture 13 of the front 12 of the cabinet, and pass therethrough to the disk 20. The particular coniiguration of the aperture 13, as herein described, will be seen to conform with the conguration of the peripheral edge of the disk 20, whereby as the disk 20 is rotated one of the slots 23 will move across the aperture 13, thus permitting light rays to pass therethrough and to be focused by the lens 18 for impingement upon the photoelectric medium 14, which acts in the usual manner to propagate or modulate an electrical current of the amplifier 15, whereby the reproducing unit of the sound propagator 17 will be energized and sound waves will be emitted therefrom.

For controlling the type of sound waves propagated by the instriunent 17, suitable physical forms as indicated at 25 in Fig. 1, may be positioned for superimposing their shadows through the aperture 13 and upon the disk 20. With such a shadow superimposed through the aperture, it will be seen that successive portions of the silhouette of the body will be permitted by the slot 23, to superimpose their eiect upon the photoelectric medium 14.

By referring to Fig. 3, it will be noted that the various types of wave front, as indicated by A, B and C in this figure, may be formed of suitable opaque material and positioned as the body 25 is positioned in Fig. 1, whereby a sound wave will be propagated by the instrument 17 in accordance with the wave front presented to the beam of light from the lamp 10. It will be seen that the amount of light passing to the photoelectric medium will vary as the slot 23 passes before the aperture 13 and that the current flowing through the photoelectric cell will be varied accordingly, and that the sound propagated by the instrument 17 will be determined by the speed at which the disk is revolving, in combination with the characteristics of the shadow of the wave front presented.

The method of propagating sound waves by the present apparatus, will be seen to include the step of illuminating the aperture 13, superimposing a shadow on the aperture, and revolving the disk 20 to permit successive portions of light to be focused by the lens 18 upon the photoelectric cell 14 and amplifying the current thus produced and propagating sound waves in response to the current.

Thus it will further be seen that the present invention provides a novel method of and apparatus for propagating sound waves and that the device has considerable usefulness in the eld of study of sound waves. The pitch ofthe tone propagated may be readily controlled by the Leesoeo speed of rotation of the disk 20, and various experiments may be carried out by superimposng the shadows of various physical bodies upon the aperture 13.

Any shadow whatsoever that is cast on the aperture produces a corresponding tone. By holding up one ringer in the path of the beam, one can produce a sound. If all ten fingers were held so as to cast a shadow of ten even crests and troughs, with the motor going at ten revolutions per second, a sound with the pitch of 1000 would be produced. Thus it is possible, by manipulating the hands in the path of the beam of light, to cause the shadowgraphs to produce an unlimited number of different tones or qualities, and even though the motor speed be constant, to alter considerably the pitch of these tones.

Another way of producing a musical scale would be to have a set of masks in a row, each mask having cut in it a greater number of wave forms than the one before it. If these masks be attached to keys so that when a key is depressed its mask will be raised up in the path of the light and cast its shadow on the aperture, then one could play different notes in rapid succession.

With this instrument, it` is possible to produce qualities of sound which are entirely new, and by manipulation of the shadows, to alter these qualities with the iinest degree of shading. The greatest virtue of the instrument as a means of studying sound, resides in the fact that one is enabled to see with the eye the wave form at the same time that it is being sounded by the apparatus. And one can hear the change in quality while observing the change in the wave form with the eye.

In considering the present method and apparatus, it will be understood that numerous changes and modications and the full use of equivalents in the construction of the apparatus as well as in the method herein described, may be resorted to without departing from the spirit or scope of the present invention as outlined in the appended claims.

Having now described the invention what is claimed as new and for which Letters Patent of the United States is desired, is:-

1. In an instrument for the production of sound from a wave-form member, a source of light, a photo-electric cell, and means for producing moving light bands between the light source and the cell, said means including a revolving light-transmitting member and a screen opening associated therewith and so arranged as to permit an unvarying amount of the light to fall on the said cell in the absence of the wave-form member.

2. The invention as in claim l the revolving light-transmitting member including a moving multi-apertured member so arranged with respect to the screen opening that the apertures pass successively across said opening.

FRANK MORSE ROBB. 

